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What did Paris' de Gaulle airport look like before the t2 expansion?
Charles de Gaulle airport (CDG/LFPG) in Paris had great expansion in the new century, including new runways and terminal 2 buildings.
What was the airport layout before the great expansion?

CDG had Terminal 1 only from its inauguration (1974) until Terminal T2A/T2B were opened in 1982, T2C/T2D/T3 around 1990, T2E/T2F/T2G after 2000. The 4th runway entered service in 1998. See this current map.

With the edit in your question, the answer is easier, before T2 there was only T1: During construction and completed.

You will hardly find anything complete on the web as :

at the time of the expansion a bunch of years ago, you didn't have that much computer assisted medias to produce representative documents.
most accurate documents are inside old books you can only access at specialized libraries, rare copies owned privately or museums.
Because Charles de Gaulle is a french airport, you'll likely to find what you're looking for in french !

I do have an Air France magazine with Charles de Gaulle history til 2002, and another dedicated to the Terminal 2F extension, but because those are copyrighted materials, I can't post them here. Sorry.
Though, you can head to the following sites :
http://www.entrevoisins.org/paris-charles-de-gaulle-de-1945-1975.aspx
(video - if you don't mind quality of the era)
http://www.aeroportsdeparis.fr/groupe/presse/40-ans-paris-cdg/photographies
(a couple pictures)
http://airinfo.org/2014/03/07/paris-charles-de-gaulle-fete-ses-40-ans-video-photos/ (dedicated copy of the above)
http://www.goussainlivres.com/librairie/librairie/aeroport-roissy-charles-de-gaulle=198.html
(one small cropped overview from a book - bear in mind that most relevant structures of the airport is inside that picture and everything around are empty areas)
Basically, you only had the Terminal 1, and one runway. Airport name was "Paris Nord" before becoming "Roissy-en-France", then finally called "Charles de Gaulle" just before inauguration (8 of March, 1974). And initial planned extensions were identical copies of the Terminal 1 all other the place including where T2 and T3 are today. Sorry, I can't post a plan from the Air France book, but it's rather similar to the one you can spot in the video above.
There are also rare documents you could retrieve from old magazines issued at the time (Air & Cosmos to name the one I know of) or magazines like EntreVoisins (used to collect them at Maison de l'Environnement, Athis-Mons, near Delta Museum) which sometimes raises issues about noise pollution from Paris Airport platforms (comparative maps of the airport through the years)

Sorry, I was reffering to "Maison de l'Environnement", not Orly Airport. But further searches lead me to realize the museum (kind of) I'm talking about isn't closed by now. I'm surely confusing Maison de l'Environnement with something else near Orly related to aviation that has either closed or ceased something important. Post edited. Thanks for the notification.

There was the delta museum (delta wing aircrafts, but not only) with a Concorde prototype, a Caravelle. Currently closed. Is that what you remember?

@mins. I thought of it aswell, as you walk right in front of after taking the bus from Paris to get at Maison de l'Environnement, but the dates doesn't match. I left Paris in late 2007 and ceased to go to the M.de.L'E less than a couple years before. I'll edit again and remove the vague assumption. Thanks

Before Edit : I were used to collect the EntreVoisins magazine each month at "Maison de l'Environnement" (which appears to have ceased issuing some copies of the magazine around 2006 or 2007, then resumed ?), south of Orly Airport. Those magazines were (are) used to bring back from history hundreds of such documents, and I vaguely remember a few with CDG airport maps in the past (noises pollutions were one frequent topic of the issues, and there were comparisons through the years) But I sadly thrown all of them to the bin when I leaved France, knowing no one willing to get the copies. :/


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Can commercial airplanes be converted to drones?
Is it possible to convert a commercial airplane into a drone, such that if a pilot fails to respond to ATC it can be remotely piloted?

Can a drone be hijacked and made to crash?

An unoverridable remote control would only turn the problem from dealing with insane pilot to insane ATC. An overridable remote control on the other hand, would do nothing in case of deliberate pilot action.

possible duplicate of On modern commercial airliners, how much of the flight could be fully taken care of by the auto pilot?

How about a remotely (ATC-)activated autopilot, unoverridable from cockpit for an ATC-defined amount of time (or until disengagement command sent from ATC)? That would solve the problem of required bandwidth and, depending on the amount of available fuel, buy some time for negotiations/interceptions/whatever. Any such command issued by an ATC should immediately brought to attention of some other ATCs, by sound alert or sth. like that, and they should be allowed to tune in on the voice conn. Multiple "downvotes" by them should make the system unlock the autopilot.

@Alexander How about some organization spends an inordinate amount of time and resources in order to crack the system. Now you have remotely controllable aircraft capable of being used (e.g. 9/11) in horrific acts of terrorism. Or, not even terrorists, some government might want the ability to control the aircraft of another government (Russia/Ukraine, Israel/Any arab nation, ISIS/Any infidel run country, etc.)

@CGCampbell Nope, remote activation/deactivation of Autopilot is not changing AutoPilot settings and won't make the plane remote-controlled. You can't control it, but the pilot cannot as well. The autopilot takes control from copilot, flies on until Dusseldorf, and by that time we hopefully have some psychatrist that can talks him out of his plan. And regarding governments, I should have mentioned that this would be purely an Airline thing. GA is completely left out, since, heck, most GA planes don't even have an autopilot...

Is it possible to convert a Commercial Airplane into a Drone

For what its worth, yes this would be technically possible however it comes with some risks.
When To Take Control: This brings into the simple idea that in an emergency the pilot may need to be in control of the situation as they often have the most information about exactly what is happening. If the plane had a serious issue and the ground controller did not know what was happening they may take control and only exacerbate the problem.
Connection Reliability: Keep in mind that planes are flying at very high altitudes moving quite fast. Maintaining a reliable connection in these conditions is difficult. Since a reliable connection is hard enough to maintain you again may create more issues than you solve. This also has to be a fully duplexed channel since the plane needs to transmit its telemetry and receive control inputs in what is more or less real time. At this point the data up/down rates would push the limits of what we can do today.
Connection Security: As mentioned you would need to secure the connection to prevent someone from taking it over maliciously. This in and of its self is a big problem. But lets not turn this into a digital security debate.
Cost: As nice as safety is its not free. Since there is currently no system in place on a global scale to do this it would have to be created. Someone has to pay for that and unless the FAA is going to require it you will have to get the airlines/aircraft makers on board with this voluntarily. On top of that any system that is added like this would have to be certified by the FAA.
So while it is possible there are very real barriers to a system like this include but are not limited to the ones listed above and before someone comes back with the "if it makes it safer than we should spend the time figuring it out" response I will mention that modern technology is as good as it is and there are already companies and individuals researching new tech like this but Keep in mind that with FAA regulations taking the time they do to get, planes are flying with tech that is now considered "dated" by the tech world.

I take issue with your points about connection security and reliability, because the military makes these connections with their drones all the time.

Yes they do but they can afford momentary drop outs as well as a more or less small fleet and thus can devote massive resources to a single drone. Doing this for every aircraft in the sky would be difficult.

And it's a drone with nobody on board. If it crashes, you lose hardware, not lives. (Understanding, of course, that if it's an armed drone, there could be a larger than expected explosion on the ground.)

@raptortech97 Regarding the military, even in the relatively short history of drones, remote control hacks have already happened, even by governments with relatively unsophisticated capabilities. Now imagine this had been an A380 instead of an RQ-170 and al-Qaeda instead of Iran. That's a pretty good reason not to do this.

@FreeMan if it's armed and you crash in the wrong area, you absolutely do lose civilian lives

@raptortech97, hence the parenthetical expression at the end...

Remote links via iridium constellations ensure that uplink is not at all problem.  Furthermore operating a drone by flying it remotely is a bit out dated.  Since sophisticated autopilots negate requirements for any link at all  except prior to touch down.

@raptortech97 I agree with Dave in that this would push the limits of current technology.  If you want a high quality Iridium satellite uplink you'll pay through the nose for it.  The kind of bandwidth and reliability we're talking about is almost too much to be even available on the civilian market.  See http://aviation.stackexchange.com/questions/2198/why-dont-all-commercial-aircraft-transmit-gps-data-in-real-time/

In order to prevent both incidents such as Malaysia 370 and Germanwings 9525, you would need a system that could have immediate and complete control of the plane, as well as impossible to be disabled by the crew.
In addition to the other reasons offered, this sounds like it would be a bad thing more often than it would help. Is the plane allowed to fly if it is not working? Who decides when to take over control? ATC? Do we trust that whole system?

Do you know something about MH370 that I don't? Been diving for those recorders have you? ;)

@falstro I too was curious as to the relevance of that incident...

Is it possible to convert a Commercial Airplane into a Drone?

Techical feasibility is just one aspect.
Let's start from what is a Drone nowadays: it is a remotely controlled aircraft.
This means that to "convert" a commercial aircraft into a drone you need:

a pilot on ground
bi-directional communication

Bi-directional communication is the "easy" part: plug in a bi-directiona antenna, write some thousand lines of code to make it usable within the aircraft system, spend years and tons of money to certify the new components and the code and you're good to go.
Now you need qualified personnel on ground continuously on stand-by, something that is going to cost (and is not given that it will popular).

Now let me add a second part:

Would it be useful?

It is not given, by reading the few official informations available ATC had no idea about the situation on board in those 8 minutes, it is not given that such a system would have been activated.

Should it be done?

I would say that the benefits are  dubious at best: you're opening a channel on every aircraft that allows them to be controlled remotely. Someone is gonna try to crack whatever encryption is going to be used, with results much worse than the original "problem".

That last paragraph for me is key to this answer!

Frederic, the following comment is not to answer the original question, but to address your " second part "  comment. If this type of  remote take over  technology was available, it  would have its advantages in some specific emergency situations, especially  for smaller type private jets where hypoxia had become the concern. The distressed aircraft could then be remotely flown to a lower altitude until the situation was stabilized or flown over an unpopulated area. ...Thank you

@garyv440 it's Federico. Anyway, my remark remains valid: would the benefit be enough to counteweight the inherent problems of such an idea? aren't there other solutions?

I'm interpreting your question as really two questions:

1. Can commercial aircraft be modified so that they can be remotely piloted?

Yes, with some hardware modifications on the aircraft to allow for command and control and telemetry data to be transmitted.  If installed as a separate system, you would need VHF/UHF antennas, RF amplifiers, FMS/autopilot interface, etc.  On the ground, a bunch of directional antennas and ground stations strategically/geographically placed to allow for maximum coverage.  Realistically, UHF communication is only going to get you out to around 150 miles or so in good conditions.  Any further than that, and you need microwave (GHz frequency) links, and even then, this is no good over the oceans due to curvature of the earth.  HF is an option, but I'm not sure how well you can use that for reliable data transmission.
The good news is that ATC towers and aircraft already have equipment that operates at these higher frequencies – the radar transponder/beacon system – however, serious modification of the system is required to make this feasible.  Aircraft telemetry requires a much wider bandwidth, and more constant connection than what's necessary to ping back with a simple four-digit code that transponders currently reply with, though it's possible, but probably at the expense of other aircraft flying in the same region, as the directional ground antenna would have to be pointed at the aircraft in question (and not constantly rotating).

2. Can ground controllers take over in the event of an emergency?

If this became a thing in commercial aviation, it would likely be at the behest of governments and their aviation authorities, not private airlines.  The sheer cost of equipment upgrades would not make, say, Delta and Lufthansa corporate types happy, but it would be very popular with equipment manufacturers like Boeing, Rockwell-Collins, and BAE.
So let's say we solved the problem of communication mechanism with the aircraft, we still need command/control equipment on the ground.  The military has long been a pioneer in the field of unmanned systems, and I speak from experience that it has taken a long time to get to the point where they are currently.  Early systems were all a hodgepodge of various protocols, datalink standards, and ground control stations, but ever so steadily reaching commonality.
One of the earliest attempts at this was the One Station Ground Control System (OSGCS), developed in the early 2000's, but even as of five years ago, was not in common use across the board, mostly due to program and fielding costs.  These costs would likely see any commercial-sector implementation at national levels, where command and control centers would house the (most) expensive equipment and the qualified operators, with a network connection to the ATC towers with the communication equipment.  In practical theory, I don't think this would go down well, but let's assume a perfect ATC system for the time being.
So then there's the security of the system.  What prevents anyone from hijacking an aircraft remotely?  Now you need to add a very good authentication/encryption mechanism, and standardize that across national boundaries.  What if it's a foreign carrier over your soil?  And good luck getting the United States to share its cryptography standards.
Then there's the human factor – what override procedures are available to the pilots, if any?  What options does the ground commander have at his disposal?
So I think it's entirely possible, but there are a ton of obstacles to overcome, and implementing this system would take years (probably decades at best) and billions of dollars to achieve.

Is it possible to convert a Commercial Airplane into a Drone?
Yes
Can it be done at will?
Not likely
Boeing has converted an F-16 into an unmanned drone (some pictures here).
Please note that it cannot be done just by the push of a button, in a case similar to the Germanwings airplane. A drone costs a lot of money, and fitting every airplane with such technology is not feasible.

Incidentally, the conversion of aircraft into drones was first done in 1935; the goal of that (and, for that matter, of the QF-16) is to be an aerial target.

Can you if you prepare for it? Yes, it's been done for both full scale crash tests NASA's controlled impact demonstration and boeing's crash experiment; the final leg of the flights was done remotely both times (you don't want a pilot in there for longer than you need to).
It requires modification of the aircraft to decode the radio signals into control inputs. But the existing auto pilot will help a lot. Doing so remotely in mid-flight is flat out impossible.

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Where are the communications antennas normally located on general aviation aircraft?
In the past I have had instructors suggest that I use COM1 in the air and COM2 on the ground. The rationale was that most aircraft have the COM1 antenna on the belly making it favorable for air to ground when in the air and COM2 on the roof making it favorable for ground to ground when on the ground.
It can definitely be helpful to use the top antenna for ground communications and the belly antenna for air.
I frequently fly a late model PA-32 and I haven't found documentation on which communications antenna is which.
I also frequently fly Cessna aircraft which usually have all comms antennas on the roof.
I sometimes fly an SR-22 and my instructor suggested using COM1 on the ground and COM2 in the air. This is reverse from what I thought was usual, but indeed the SR-22 AMM shows that the COM1 antenna is on the roof with COM2 on the belly.
Is there really a rule of thumb here or does it vary so much from one aircraft to another that no rule of thumb is possible to say?

Your best bet would be to follow the guidance found in the POH.  Any A&P mechanic should be able to answer your question on the PA-32.

On the PA-32 I haven't found an answer in the POH. As far as asking the mechanic, I want documented answers in this case.

@RyanBurnette, if all else fails you can always ask your mechanic and then post the result (answering your own questions is OK and even encouraged here).

Sure thing, if my mechanic gives me some documentation I'll post it.

@RyanBurnette "documented answers" would mean "Call your mechanic or avionics tech and have them trace the wires and find out": Your aircraft has almost certainly had its avionics modified over the years, so unless you examine the aircraft and determine this empirically you have about a 50/50 chance of guessing right.

No this particular PA-32 hasn't had the radios, antenna cables or antennas modified since factory. I'm still mainly interested in if there's a rule of thumb for this and the only evidence of a rule of thumb I've seen is the documentation from the Cirrus AMM.

Honestly? That AOPA article overstates the issue of airframe shadowing (at least for light GA singles): Both antennas will usually work fine on the ground, and will probably work without any issues in the air as well.
Airframe shadowing can cause issues, but if it were as big an issue as people like to make of it there would be no aircraft with single-radio installations (because they would either not be able to talk to people on the ground, or not be able to talk to people in the air).
There are plenty of aircraft flying around with only one radio.
If you're concerned about whether your transmissions are readable pick a nice quiet time of the day and ask the tower for a radio check on Com #1, then repeat the process on Com #2. (Because we're talking about AM radio the results of this test are valid for your aircraft's position and heading when you did the test, and in weather conditions similar to those the test was conducted.)

The general rule of thumb is that each radio will be connected to a separate antenna (this is necessary if you want them to work independently). Some avionics shops have a preference of which way they wire things, and I'm sure manufacturers have a standard they use in their shops (either the POH or the maintenance manual for your aircraft MAY tell you what the manufacturer's standard is; it may also be noted on the FAA Form 337 for the avionics installation if one was filed).
I've seen varying combinations of which radio is connected to which antenna ("Single radio - Antenna on top" ; "Single radio - Antenna on bottom" ; "#1 Left Wing, #2 Right Wing" ; "#1 Top-Front, #2 Top-Rear", "#1 Top/Ground, #2 Bottom/Air" ; "#1 Bottom/Air, #2 Top/Ground").

Great answer. My routine involves using COM1 for tower/appr, COM2 for atis/ground. The only time I vary that is when I only have 1 good radio. Bottom line, it probably doesn't matter enough to worry about it or enforce a particular procedure on a student. As long as they have something that works.

In general, while choosing the antenna locations the following considerations are taken into account:

Obstruction of the signal by the aircraft (components).
Interference
Structural issues like vibration and flutter.

In general, if the aircraft being operated from a towered airport is fitted with two radios, it is advisable to have the antenna for COM1 on top of the aircraft and COM2 on the bottom, with a separation of at-least one meter.
Also, usually, the top antenna is used in ground and the bottom antenna is used for air to ground communication as VHF (or UHF, for that matter) is line of sight. Note that it does not matter whether the COM1 antenna is on top or bottom; the top antenna is usually used for on-ground communication (sometimes, this doesn't work, as the tail plane might obstruct the signal). Another reason for using top antenna is that the bottom antenna could be damaged in case of hard landing.
As long as the antennae don't suffer from 'shadowing' of the aircraft, it can be located anywhere. A good example is the location of antennae in case of homebuilt aircraft from kits, where the both the antenna could be on top or bottom or even have a single antenna for the same model.
In the other extreme, the (avionics) manufacturer may prescribe a particular installation location for the antenna (usually for COM1 on top). Also, in some aircraft, the VHF radios will use both the upper and lower antenna. The signal is switched between the upper and lower antennas with coaxial relays, with the top antenna used while on ground, while the bottom one is used in air.
Also, the HF antenna is usually on the vertical tail and GPS antenna on top of the fuselage (for satellite signal reception). The antenna are mounted on the aircraft plane of symmetry or symmetrically to the either side of it (like Cessna 150).
For a short answer to your question, in general aviation aircraft, the location of com antenna is immaterial as long as there are no communication issues.

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How does the Pratt & Whitney Canada PT6 differ from other turboprop engines?
As far as I know, all turboprop engines have mechanical continuity between the engine and the propeller except for the Pratt & Whitney Canada PT6 family of engines. What is the correct term for the setup the PT6 uses to power the propellor and how does the PT6's design differ from other turboprop engines?

I can't actually find the term “direct drive” used with turboprop engine anywhere, only with turboshaft. Also as far as I can tell, the layout of PT6 is pretty typical (separate gas generator turbine and free power turbine, reverse flow so the shaft from the free power turbine does not need to go through or around the engine).

Good call. I'll edit "direct drive" out.

That does not necessarily mean the term would be incorrect. Just that it is not common.

After thinking about it, it might be considered incorrect. When the term direct drive is used with piston engines the propeller is attached directly to the flywheel. No turboprop engine can work without a reduction gear. Even if there's mechanical continuity it's not really direct drive.

I don't think there is any difference in mechanical continuity. Some early engines might have had the propeller on the same shaft as compressor, but all the modern ones use free power turbine where the low pressure turbine only drives the propeller and high pressure turbine (or high and intermediate pressure turbines) drive the compressor. So turning the propeller won't turn the compressor and starter won't turn the propeller.

@JanHudec A quick google seach located several references to "direct drive" turboprops such as this one. They all use the term to refer to a single shaft engine as opposed to a "free turbine." This pdf actually uses "direct drive" to refer to the fuel pump system.

@JanHudec I'm not sure if I agree with everything you said there based on what I understand about turboprop engines, but I do think removing the "direct drive" reference had an overall positive impact on the question.

@TomMcW, that makes sense. But according to that definition PT6 is not unusual, because most turboprops have free power turbine.

there is no direct drive there is gear box to the propeller but i think there will be some torque issues i dont know how thy solve that detrimental problem

Split Shaft
Several turboprop engines, including the PT6 turboprop engine, use an epicyclic gearbox only, many other turboprop engines use a multishaft gearbox. The latter usually results in the propeller axis being offset from the turbine axis.
In common with some other engines, the PT6 turbine is also reversed. This facilitates the split-shaft arrangement where the engine and propeller are driven by separate (but in-line) shafts, each connected to their own turbine wheel.

PT6

Image: P&W

Image:12Charlie
A contrasting and common design

Image:12Charlie

I'm trying to understand how any turboprop/shaft with a gearbox can be described as "direct drive". Any help?

@egid: I imagine it means that there is a continuous metallic contact through the power train from compressor to propellor. This is not the case in the PT6.

Ah, I see. That would make some sense.

I think "direct drive" was the wrong term to use here. I edited it out of my original question.

I don't think the layout is truly specific to PT6. Reverse flow is used in the other small turboprop engines too, at least in Allison 250/RR M250 and Walter M601. The layout of Allison 250 is rather complicated with two-shaft gearbox and compressor in the front, but at least the Walter M601 seems to have the same layout as PT6 with split shaft and in-line planetary gearbox. The layout does not appear in large engines, probably because turning larger air mass flow is no longer practical.

@Jan, Thanks, I'll update the answer to include that point.

@Jan: Often, the large engines borrow their hot section from turbojets or turbofans. Also, their diameter would grow too big for a clean aerodynamic design.

The difference is quite simple , with the Pratt and Whitney design there is no direct mechanical link between the turbine compressor and hot section to the propeller gearbox reduction drive . With  the Allison design were you to turn the propeller by hand all the turbine parts will move all the way back to the inlet compressor . There is a direct mechanical link all the way through

As described above, it's a split shaft turboprop engine.  The design isn't unique to the PT-6 (T-74) but the PT-6 variants are by far the most ubiquitous split shaft turboprops on the market today.


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Are there any helicopters equipped with pressurized cabins?
I would think that a pressurized helicopter is impractical since helicopters are usually flying at low altitude, but has a pressurized helicopter ever been conceived or built?

Bell Helicopter BA609

An unmodified helicopter with a gas turbine engine landed on the summit of Mount Everest in 2005. It was a Eurocopter AS350 B3. AFAIK the pilot used oxygen, and the helicopter was not pressurized.

The weight and the price would need to be justified by some high altitude mission for which an O2 mask is not appropriate. What could that be, given the low ceiling of such aircraft? Imagine an airplane pressurized door. A loss of pressure could occur instantly due to the small volume, that's another show stopper.

Helicopter cabins are not usually pressurized as they are not expected to be operated at high altitudes.
The largest operational helicopter, the Mil Mi 26 Halo has a pressurized crew cabin.
The Russian Mil Mi-24 Hind and Mil Mi 28 Havoc feature pressurized cockpits. However, these are for operating in an NBC environment, not for high altitude operation.

What is an NBC environment?

@RyanBurnette Nuclear, Biological and Chemical- A condition where there is a possibility of contamination due to radiological, biological or chemical agents, usually in war.

Is that a small overpressure with free (uncontrolled) release of the air in excess, or a fully airtight system?

@mins It is of the overpressure type, atleast in the combat helicopters.


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What alternatives to pitot static systems are available or in development?
Air France 447 is a powerful example of what a serious situation unreliable air data indications can be if not handled properly by a crew. Still, whether crews are properly trained or use that training, unreliable air data presents a dangerous situation. Pitot tubes are fallible devices susceptible to errors caused by environmental factors such as ice crystals. With this in mind, what technical alternatives to pitot static systems exist or might be developed that are more accurate and less prone to interruption?

Although used for stealth, and susceptible to water even in its liquid form, here's another system

Of course, any novel alternative type of sensor may also be susceptible to problems due to ice or some other conditions we don't yet understand. You'd potentially be replacing a known risk with some unknown risks.  The BEA report on AF447 did not mention or recommend looking for alternative sensor technologies - it discussed the use of other types of pitot-tube.

@RedGrittyBrick That doesn't mean they couldn't be used in conjunction with each other. The article Aeroalias linked points out that the failure modes of the optical system were different from those of pitot tubes. Therefore they would be a good complement to each other

A number of systems are under development- most are optical systems- determining airspeed using LiDAR. NLR, for example has developed an Optical Air Data System for this purpose:

The  developed  system  applies  the  LiDAR technique to measure air speed in four different directions. The aircraft’s TAS (True Air Speed),  AOA  (Angle  Of  Attack)  and  SSA  (Side  Slip  Angle)  are  calculated  from  these  speed  measurements.

Other systems are in prototype stage- including a photonic system that is based on back scattering of light, but none of them are yet operational.

While there are different possibilities to measure pressure (e.g. pressure sensitive paint), all can be influenced by environmental factors.
So the question might be: What is the best trade-off between cost of the sensor(s) and reliability of the whole measurement system?
One solution might therefore be to compare different sensor readings (Air speed, control surface position, weight,  altitude etc. ) and compare those with a (machine learned) model of how the aircraft should behave. This would enable a algorithm to decide if a sensor does not provide realistic data and should therefore not be trusted any more.

It actually reacts to a change in the partial pressure of one air component (oxygen) with a change in color. So one could have a small patch of glass which is looked (sensor) at from the inner side.


text:
Is it possible or has anyone explored the possibility of capturing static electricity for supplying electrical loads on an aircraft?
I am wondering if it's possible to harness static electricity generated on the skin of the aircraft to supply power for system loads? Has anyone ever undertaken a project to achieve this?
One reason the question came to mind is that all aircraft I've ever seen have static dischargers for the purpose of dissipating it.

P-static energy source for an aircraft and Airbus Energy harvester, aircraft component comprising the energy harvester and an aircraft comprising the energy harvester or the aircraft component

@mins, hm, interesting. Does it say how much energy it can actually collect? Normally the potentials are large, because air is pretty good insulator, but I wouldn't expect the charge to be enough for anything useful.

@JanHudec: These applications are to charge small capacitors, likely to then power small wireless devices. The amount of static electricity will depends on many factors, but is very small. Also if the aircraft is seen as a generator of current electricity, its internal resistivity is very high and as soon as current is flowing the very high potential falls near zero volts. I've posted a link to a study below your answer. From it: "The typical charging rate of a B-17 flying at 200 mph in snow was 100-155 μA", that is half a coulomb per hour.

No, it is not.
To use electricity to do work, you need:

two thigns with stable potential difference,
large amount of charge and
good electrical connection to both terminals

And static electricity does not really give you either:

the amount of static electricity collected depends significantly on atmospheric conditions,
the total charge collected is tiny even though the potential increase can be huge and
one of the terminals is outside air and the electrical connection to it is really poor (if it wasn't, charge couldn't accumulate on the plane).

@RyanBurnette, there is slight problem that I don't really know typical numbers. But it is pretty similar to static electricity you encounter at home: even tiny spark requires thousands of volts to happen and you can easily collect that on your sweater—but than that one tiny spark equalises the charge and there is nothing left to power anything.

That clears up my question. Thank you.

Some information about the charging amount A Critical Review of Precipitation Static Research since the 1930's


text:
How can the Pipistrel Apis land safely?
I just saw a photo of the Pipistrel Apis motor-glider, and it got me wondering: How can it safely land with only 2 wheels total? To me it seems that falling to the side would be inevitable, and with wing fuel tanks, that could be terrible. In all the pictures, it's resting on (one of the) wingtips.

Are the wings/wingtips reinforced for landing & supporting the airplane on the ground?

This motor glider only carries 5.2 gallons of fuel, about 17 pounds on each side, tucked right up against the fuselage. That's not much weight on the wings.

Just as a sidenote, the U-2 spy plane also only has two center mounted wheels and seems to tip on to one wing after coming to a stop. See landing video.

Added the name of the plane to the title - this would help searchss (Google/Bing)

Many modern gliders only have one wheel -- two is a great luxury!
In a glider the wing and flight controls remain effective until the aircraft is almost completely stopped - with a little training and practice it's possible to balance on the one (or two) wheels right up to the point where you're nearly stopped, at which point the glider will gently tip onto one of its wings as it comes to a halt.
As you've surmised the wingtip usually has some reinforcement or other provision (such as a skid plate or a small wheel) to prevent damage when it contacts the ground. The photo below is of one of these wingtip wheels.

Oh I'm really surprised by that. I'l rethink the idea of learning to fly a glider now, haha!

@wingleader It's also worth noting that the Apis fuel tank used to be located in the fuselage -- they moved it  out into the wing for safety reasons (so you're not sitting on top of 2 gallons of fuel if you crash).

Landing and taking off in a crosswind also requires a fair amount of skill, versus an airplane. At many glider ports you have a ground crew that holds the wing level until the tow plane starts its ground roll. But if you don't have a ground crew, the wing drags as you put in full opposite aileron to get the wing off the ground. Once it comes off the ground, you have to fly it wings level or with the upwind wing low enough to keep the plane rolling straight.

Don't forget the wind: Even when the glider has come to a stop, some control power remains depending on headwind. BTW, the real luxury is the tip wheel in the picture. Normally the wingtips have small rubber blocks with a steel plate screwed to its bottom.

Looks like someone stole that wheel off his kid's inline skate! Now poor Timmy will be wobbling down the sidewalk instead of doing tricks down the stairs.

they come from the same place that Citabria tailwheels do: BBQ grills

Almost every glider has just one wheel close to the centre of mass. Some have a small tail wheel, school gliders may have a front wheel that avoids to scratch the nose when you are learning. Whatever the number of wheels is, you spend most if not all the time balancing on the main one.
Every skilled glider pilot is against anything that could create even the minimum amount of drag and is not strictly necessary!
The key point here is the amount of fuel inside the wings, which is really tiny (a small motorbike tank per wing) and allows for safe landings. If it was more it could create problems mostly because of its weight and the related stress on the wings when touching down. Indeed most of the competition gliders allow to fill their wings with water in order to increase the performances at high speeds, however it is mandatory to evacuate it before touching down, and of course you wouldn't want to do the same with unspent fuel.

How would the tanks be completely emptied of water, or do they resign to never filling them with fuel afterwards? (or does a small amount of water not destroy the engine, similar to what would happen in a car)?

@user2813274 Competition gliders I'm familiar with do not have engines (it's wasted weight).

@user2813274 Water goes in dedicated tanks that can fill all the wings and you release it by gravity before touching down. Fuel tanks (when present) are tiny and close or inside the fuselage.


text:
What weapons do A-10 Warthogs typically carry?
What is the A-10 Warthog's typical operational load out? Seeing as it is built a tank buster, does it actually carry anti-tank weapons, and what situations would they be used e.g would they (A-10's) ever use an AGM or ASM on a tank?

The 30 mm GAU-8/A Avenger  with over 1000 rounds is in itself a potent anti-tank weapon, which can fire depleted uranium rounds, among others. It carries a number of anti-armor weapons like the AGM-65 Maverick, Hydra 70 rockets and cluster bombs in 11 external hardpoints with a maximum load of 7200 kgs.
The 'typical' operational layout of aircraft depends on the mission. For example, the image below shows one configuration.

By U.S. Air Force photo by Master Sgt. Blake R. Borsic - http://www.af.mil/shared/media/photodb/photos/000217-F-0656B-004.jpg, Public Domain, https://commons.wikimedia.org/w/index.php?curid=505075
In the above picture, the aircraft can be seen carrying a ALQ-131 ECM pod under one wing and two AIM-9 Sidewinder air-to-air missiles under the other wing for self-defense, along with AGM-65 and bombs. If these are not required (for example, where there is little danger from anti-aircraft fire), they can be replaced with others or the aircraft is flown without one so as to increase range/time on target.

By U.S. Air Forces Central Public Affairs Photo by Master Sgt. William Greer - http://www.flickr.com/photos/dvids/5510306058, Public Domain, https://commons.wikimedia.org/w/index.php?curid=37832505
In this photo, we can see the aircraft carrying only precision munitions and targeting pods.

The A10 was designed around the GAU8/A cannon, but once the aircraft entered service it was realised that a stand off weapon was needed to give the aircraft a reasonable chance of survival in the face of the Soviet short range air defences. This led to emphasis on the use of the AGM65 Maverick missile, which over time was upgraded with an imaging infra-red sensor and other improvements to increase it's effectiveness in typical European weather conditions.

It has a 30mm cannon with depleted uranium rounds.

It carries more than that.


text:
Are private jets allowed to land at London Heathrow?
Heathrow is among the worlds busiest airports, with traffic mostly (entirely?) from airliners. Are private/business jets (e.g. Gulfstream G650 or Cessna Citation X) allowed to land at Heathrow?
If so, what are the landing fees and what criteria do they use in charging them?

Please tell me you're not typing this from 40,000 feet above London.

im not typing this from 40000 feet above London

Please tell me you're not typing this from Heathrow's holding cells.

Please tell me you not Airport intelligence cause you'll foil my escape plans

The answer appears to be "yes", but unless you're transferring directly from the private jet to/from an international flight in/out of Heathrow, it's a poor choice. Fees are high and delays are common.
With no fewer than 13 other airports to choose from, chances are that one of the others will be a better choice. Luton and Farnborough are the most popular choices for private jets.
Reference:
PrivateFly: Inside London Airports - Private Jet & Helicopter charter

And supposedly Biggin Hill now too! So much so they're closing it to GA traffic :(

Thirteen if you're prepared to call places like Oxford, Farnborough, Stansted, Southend and Cranfield "London"...

@DavidRicherby: Well, granted--some of them are probably stretching "London" right to the limit and perhaps a bit beyond. On the other hand, some of them are quite a bit closer than Heathrow as well (e.g., London City Airport isn't just close--it's right in the middle of things).

Seems like if I was the kinda guy with a private jet I wouldn't be worried about a few grand on landing fees...

@corsiKa: Seems to me that if you didn't care about cost, London City Airport would probably be your first choice. Probably a few people who have jets but still care at least a little about costs though...

@JerryCoffin I'll keep that in mind. Step 1) Become a billionaire.

@corsiKa In general the people who are billionaires tend to care at least a little about costs. It's usually a part of how they became billionaires.

@JerryCoffin - I suppose another factor is that time is money, and the proximity of London City Airport to central London makes it a strong contender when your time is limited and money is no object; for example, London City Airport is only about 4 miles from Canary Wharf (or a short ride on the DLR), while Heathrow is more than 20 miles (or at least one change on any train/tube you care to mention).

Yes, Private jets can land at Heathrow.
Charging is based, like many airports, on aircraft weight in the first instance, but also incurred are handling charges, parking charges, and extra charges for noise/emissions rating, as well as a different price for night landings. Many airports use similar pricing structures.
Heathrow publishes their landing charges, so you can go and calculate the total cost for next time you ask your Pilot to land you there!

An interesting paragraph: 3.2 Parking is free between the hours of 2200 and 0559 UTC (GMT) from 1 April to 31 March.  Do I take that to mean that they do charge for overnight parking the evening of March 31 only?  If it's year-round, it's an odd way to phrase it.  I'm not sure how to parse it otherwise.

@Tristan looks like it's a copy paste edit from the note about night landing charges

@Tristan I was about to query this - it makes no sense!

@Tristan It's so they can keep the provision and wording in place to ease changes in the future. That way, one, the numbering remains the same, and two, they can change just a simple number as an adjustment to a discount, rather than instituting a new fee.

The short answer is :
You could. But GA traffic is heavily discouraged both in terms of fees and policies.
Longer answer:
Most of the time, the only private jets you'll find at Heathrow are those operated by heads of state and their respective governments who, for whatever reason, feel they absolutely must land at Heathrow.
Most private private jet traffic that needs to be as close as humanly possible to Central London goes to RAF Northolt.  A military airfield that's (pretty much) the same distance to Central London as Heathrow.  But its far less busy than Heathrow (and probably cheaper too, I don't know the prices off the top of my head).
The added benefit of Northolt is that security is (obviously) MUCH higher than Heathrow.  Which makes the job of keeping your VIPs safe (and the paparazzi and unwashed masses away from them) much easier.
Military needs obviously take priority at RAF Northolt in terms of availability, but most of the time its not a problem.  The RAF do most of their stuff from bases outside London out of respect for the NIMBYs.

RAF Northolt is also where the No. 32 (The Royal) Squadron is based, which provides air transport for the Royal Family and the UK Government, so its security is not just higher by virtue of being a military airbase, but a military airbase that specialises in air traffic of VIPs.

@Myles Fair enough comment, but without going into detail, the sort of security elements I was thinking of in this context would be common to all airbases. Without going into details on a public forum, the security handling and general experience of private VIPs at Northolt is somewhat different to the treatment given to Windsors and UK Government.  What private VIPs experience would be experienced at any airbase.


text:
Why doesn’t runway 31R at JFK have a VGSI?
All of the runways at JFK have a PAPI except 31R.

Why does 31R not have any kind of VGSI?

See this answer.  PAPI's are usually placed at the touchdown point for the runway.  By looking at this satellite photo you can see that the touchdown point is at the intersection of 31R and 22R-04L so there is no room for the PAPI.

The PAPI's for all the other runways are placed just short of the 1500 foot marker. The same placement here would put them past 22R. There must be some other reason

@TomMcW:  You appear to be correct about the placement of the other PAPIs.  They must make allowances for eye-to-wheel height of some larger airplanes.  In that case there appears to be a runway hold sign at the location where the PAPI would be.  Perhaps that is the reason.

If you want to, you’ll find a place to mount it. I know a small airport where it’s in front of the RWY threshold mounted on top of street lights of an adjacent street, then you just have to fly the last 50m without glidescope indicator – there is always a possibility to put it somewhere.

license: Creative Commons - Attribution Share-Alike - https://creativecommons.org/licenses/by-sa/4.0/


text:
How does one test a stall warning during pre-flight?
As a pilot, if your preflight inspection includes testing the stall warning system, how is that done?
A recent question about ADs brought up AD 68-17-04, which requires pilots to test the stall warning system for proper function as part of the preflight inspection.
How would this test be done? How would other types of stall warning systems be tested?

What kind of aircraft?  What sort of stall warning system?  Small aircraft (e.g. C150) with a pressure tube?

@Simon The question arose from Jonathan's answer on another question which was referring to a Cessna. Wouldn't mind knowing about the big planes too. Not sure how you would test either without airflow over the sensors.

Related

Stall warning systems generally function on the principle of measuring pressure distribution or angle of attack. As each aircraft will have a different type of stall warning system, the necessary test will vary by aircraft as well. Here, I will answer based on aircraft that I have experience with, but these concepts should cover the majority of light aircraft.
Aural stall warning systems can generally be divided into two types, pneumatic and electric.
Pneumatic
Pneumatic stall warning systems are found in many light Cessna aircraft, including the 172 and 177. The following system description is from the Cessna 177 Maintenance Manual:

The system is composed of an adjustable plate on the left wing leading edge, connected to a reed type horn by means of plastic tubing. The horn is actuated approximately 5 to 10 miles per hour above stalling speed as a negative air pressure area at wing leading edge causes a reverse flow of air through horn.

See this excerpt from Figure 15-6 in the C177 Maintenance Manual depicting the pneumatic stall warning system and it's location in the aircraft:

To test this type of system, air must be drawn out of the system through the leading edge scoop located in the left wing. The maintenance manual and AD 68-17-04 call for a test procedure as follows:

Prior to flight, test the pneumatic stall warning system and determine if it is functioning properly, [...] by covering the opening in the left wing with a clean cloth, such as a handkerchief, and applying a slight suction by mouth to draw air through the horn. A properly functioning horn will provide a sound that is clearly audible.

The sound is something like that from a kazoo. In actual practice, speaking personally and from my observations, the "clean cloth" is typically dispensed with.
Alternately, a Stall Horn Tester is available for a small price if you would rather not have to put your mouth on a strange airplane.
Failure of these systems will typically be due to a problem either with the horn—such as a loose reed, or with the leading edge scoop—such as a cracked or misaligned scoop.
Electric
Electric systems operate on some of the same principles, but use a movable tab—instead of pneumatic suction—to sense the change pressure distribution. This type of system is found on aircraft such as the Cessna 182, Piper Cherokee, and Beechcraft King Air.
The system operation can be generalized as follows: pressure changes cause the tab to move up thereby sending an electrical signal which will sound a horn in the cockpit. In some cases the tab actuates a microswitch. In more complex systems the tab actuates a transducer which signals a stall warning computer.
The simpler of these types of systems can typically be tested with aircraft electrical power on by manually lifting the tab and listening for the warning horn. With the more complex King Air system, testing is accomplished with a switch in the cockpit which tests the circuitry and horn. In this system, signals from the stall warning transducer are blocked out by a weight on wheels switch when on the ground, with the effect that lifting the tab will not allow for system testing.
Flight Safety (FSI) offers the following system description in their King Air 200/B200 Pilot Training Manual:

The stall warning system senses angle of attack
  through a lift transducer actuated by a
  vane mounted on the leading edge of the left
  wing (Figure 15-10).
Angle of attack from the lift transducer and
  flap position signals are processed by the lift
  computer to sound the stall warning horn
  mounted on the copilot’s side of the cockpit.
  The horn sounds when the following conditions
  are present:

Airspeed is 5 to 13 knots above stall,
  flaps are fully retracted.
Airspeed is 5 to 12 knots above stall,
  flaps are in the APPROACH (40%)
  position.
Airspeed is 8 to 14 knots above stall,
  flaps are fully extended.

The system can be tested prior to flight by
  placing the STALL WARN TEST switch, located
  on the copilot’s left subpanel, in the
  TEST position. This simulates a stall condition
  and sounds the warning horn.

Figure 15-10 from the FSI King Air 200/B200 Pilot Training Manual
Other Systems
Other types of systems exist with which I have no actual experience, either as a pilot or mechanic. I offer the following information without much real knowledge of it, but hopefully with good sources. Others more knowledgeable than I might be able to verify it.
The Boeing 737 has a stick shaker type stall warning system to provide the required warning, rather than an aural warning system. The SmartCockpit.com B737 NG Warning Systems document gives the following system description:

Stall Warning System
The stall warning "stick shaker" consists of two eccentric weight motors, one on each control column. They are designed to alert the pilots before a stall develops. The warning is given by vibrating both control columns. The system is armed in flight at all times. The system is deactivated on the ground.
Two independent, identical stall management yaw damper (SMYD) computers determine when stall warning is required based upon:
• alpha vane angle of attack outputs
• ADIRU outputs
• anti-ice controls
• wing configurations
• air/ground sensing
• thrust
• FMC outputs
• mach compensation
The SMYD computers provide outputs for all stall warning to include stick shaker and signals to the pitch limit indicator and airspeed displays and the GPWS windshear detection and alert.
Two test switches are installed in the aft overhead panel. Pushing either of these initiates a self-test of the respective stall warning channel. The No.1 activates the Captain stick shaker, and the No.2 activates the F/O stick shaker. Either stick shaker vibrates both columns through column interconnects.

The same document further defines the test procedure:

STALL WARNING TEST Switches
Push – on ground with AC power available: each test switch tests its respective stall management yaw damper (SMYD) computer. No.1 SMYD computer shakes Captain's control column, No.2 SMYD computer shakes First Officer's control column. Vibrations can be felt on both columns
• inhibited while airborne

And I thought that the pilot was just kissing his plane good night

The occasional insect you will ingest is good protein. The taste isn't so great through.

@Terry I still always associate the stale taste of stall warning air with Zep, due to our cleaning methods at my flight school.

I guess it's implied by your answer, but it might be good to mention that for planes that don't have the stall warn test switch, you just push the tab on the leading edge while the power is turned on, which should then cause the horn to sound.

This is a great answer.

You can use a stall horn tester for a small Cessna-type suction warning:

As the product description points out, this keeps you from needing to put your lips on the potentially buggy leading edge and sucking who-knows-what out of it.

Please cite your image source. It appears to be the Sportys.com product I linked to above, in which case all content is copyright.


text:
Can a plane fly backward if its propeller is in reverse?
I would like to know if a prop plane, for example the P-51, could be able to fly backward. Is it possible through some trick like changing blade angle or reverse the prob rotation direction? It would have been hard for piloting, but is this theoretically possible?

it can't doesn't have that talent to do that, but their are planes that can actually fly backwardsArticle about a plane that can physically fly back words Also flying backwards limits the thrust of an airplane so even if it can do this it wouldn't have a lot of lift and has a high risk of stall.

You don't need to apologize about your English a lot of other people on this website don't know much English either so no reason to apologize and your English isn't bad because I understood the whole question.

From my Kerbal and RC flight knowledge, if your center of gravity is behind the center of pressure, your aircraft becomes extremely unstable. Normally the CG is in front, so if you rotate the direction of airflow, all things equal, bad things happen.

The propeller would not work if rotating in the other direction. Contrary to the wings, the blades would probably stall in any case. But the pitch of the blades could be reversed without changing the rotation direction.

@Ethan: The AN-2 does not fly backwards. It has a minimum forward airspeed that is less than a very strong headwind. This produces a negative (backward) ground speed not airspeed. The aircraft is still moving forwards in the air and its propellor is propelling it forwards through the air, not backwards.

Somebody ought to mention the Harrier among all the "No" answers. Of course it's not relying on its airfoil for generating lift while doing so, so it's probably another cheat... https://www.youtube.com/watch?v=bKQlxCbaRQ4

Does mounting propeller on plane rear count? :) (Pusher configuration, eg. Kyushu J7W)

Well also the wings would be working against you as the trailing edges suddenly become the leading edges, pushing the plane down instead of lifting it up.

Related piece of trivia-- typically, a radio-controlled model airplane will still fly if the prop is put on backwards so that the "sharp edge" is leading and the "rounded edge" is trailing. So the prop airfoil is still creating some thrust, i.e. lift, in this configuration. However, the performance will be greatly reduced. Now, as for the pitch-wise stability of a whole airplane flying "backwards"? I'd say there had better be a computer helping it all work out ok.

I've also seen a photo of a model airplane where the entire wing assembly, which had dihedral, was rubber-banded on to the fuselage upside-down and backwards, so it had anhedral and so the sharp edge was leading and the rounded edge was trailing.  Reportedly it did still fly.

Fly? No.
Wings generally only produce enough lift to keep an aircraft aloft when air is flowing over them in their intended direction. If you reverse the airflow over the wing (by moving backwards in the air, for example) the wing would no longer be producing the necessary lift, and the aircraft would "descend at an extremely rapid rate" until a normal airflow over the wings was restored. (That's the polite way of saying "the darn thing falls out of the sky like a rock!")
Move? Yes. At least on the ground.
This has been demonstrated on more than one occasion by Fat Albert, the C-130 that supports the Blue Angels.  While the propellers themselves do not reverse, the blade pitch is changed to produce reverse thrust (slowing the aircraft the same way thrust reversers do on a jet engine, and in this case reversing its direction of travel).

Note that there is one notable exception to the "airplanes can't fly backwards" rule, which the article Ethan linked to alludes to: If the wind velocity exceeds the aircraft's stall speed it's possible for an aircraft to "fly" at its minimum airspeed, but be moving backwards relative to the ground.
This is a bit of a cheat though: The airplane still thinks it's flying forward (the relative velocity of the wind over the wings is in the "normal" direction, and the airspeed is fast enough to create enough lift to sustain flight). It just happens the the airspeed includes a headwind component sufficient to give the aircraft a net "negative" groundspeed.
The hypothetical P-51 in your question would require sustained winds of about 83 knots to make this trick work (we generally call that a hurricane), but something like a Piper Cub can do it at much more reasonable wind speeds.

Plenty of turboprops have the same ability to reverse blade pitch, reversing thrust. It's a requirement for the larger turboprops using L'Esperance on Saint Martin; there's no taxiway entrance at the threshold on either end and no room to turn, so aircraft that need the full runway to takeoff must powerback from the entrance to the threshold.

@KeithS Most turboprops can do it (at least the multis) - Fat Albert just does it with style :-)

@voretaq7 I guess an alternative question might be: Is it possible to design an aerofoil that can provide lift efficiently in both forward & reverse flow directions?

@curious_cat: That is a good question. Go ahead and post it ;-).

+1 for the cheat.  The number of times I have to explain to people that the aircraft might be moving backwards relative to the ground but is still flying forwards.

@JanHudec Done! Asked. :) http://aviation.stackexchange.com/questions/19122/aerofoil-that-gives-reasonably-good-lift-for-both-flow-directions-forward-and-b

"we generally call that a hurricane" Or a jet stream/jet streak. I've been on flights that had ~170 mph tailwind before coming back to the U.S. from Asia.

I just joined this site so I could give you +1 for "descend at an extremely rapid rate".  I have never seen a more poetic description of plummeting to certain death.

The C130 demo is not a special trick done only by "Fat Albert". I've seen a few occasions in the UK where a C130 taxied in reverse all the way from landing to its parking spot, rather than turning round as in the video (and then having to turn round again to depart). The cargo door is opened (as in the video link) and a crew member standing on the ramp "steers" the plane by giving instructions to the pilot over the intercom.

Even on the ground, as in the C130 demo, the aircraft and engines need to be designed to do this safely. We one had some strange engine problems in just one airline operating a widely used narrow-body aircraft. The cause turned out to be that they regularly used reverse thrust instead of a tow truck to push back from the ramp at some airfields.  Some of their pilots were in the habit of "gunning the engines" while doing that, and going outside of the design conditions for using reverse thrust.

I think the OP's understanding of a prop "in reverse" is "turning the other way around" rather then a pitch change. You might want to point that out to be sure that it's clear that spinning the prop the other way around won't do anything, as it is the same problem as you described in your first paragraph.

If we talk about the "cheat" by having a negative ground speed, the Antonov AN-2 is a great example. Despite its relative large size for a "bush plane", it has practically no stall speed: you can reduce its air speed until it basically behaves like a parachute. This means you can fly with it backwards even in a relatively mild headwind.

The Harrier can fly backwards using it's thrusting nozzles. Well it's more hovering on pure thrust than flying via airfoil lift.

In short, no.
First, the wing of an aircraft is designed to produce lift in only one direction. Airflow moving backwards over the airfoil would not be directed around it properly; the air coming across what's supposed to be the trailing edge would be divided too cleanly (so it could stall too easily) and wouldn't be accelerated as quickly by the gentler slope on what's supposed to be the back side of the wing, thus reducing lift. The leading edge, now the trailing edge, would increase drag and further reduce lift as the boundary layer would separate too soon along its curve. In other words, a wing moving backward produces very little lift and much more drag, both bad for an airplane trying to stay in the air.
In addition, most propeller-driven aircraft have their wing chords angled slightly upward from the thrust vector of the engine, which provides a nonzero angle of attack in level flight. This provides more lift at the cost of slightly higher drag, and allows a plane to maintain altitude more easily at cruising speeds with the nose level. In reverse "flight", this would end up a negative angle of attack, reducing lift even further.
Lastly, the horizontal stabilizer is designed to provide downforce in forward flight to counteract a slightly forward center of gravity (this basic design causes desirable stall behavior, causing the plane to nose down to restore normal airflow). This is accomplished in low wings with a slight downward angle of the horizontal stabilizer (or a slight up-angle to canards), and in high-wings by using the downwash from the wing to push on the tail. Moving backward, there's no downwash to balance the weight at the nose, and a downward cant would actively push the tail up as the wind moved past it, in either case flipping the plane into a nose-down attitude (also a desirable recovery behavior if you find yourself hanging by your prop).
In a stellar engineering choice by aircraft designers, they orient the curve of the wings and trim the horizontal stabilizers to produce lift and balancing trim force when the aircraft is moving in the direction its occupant(s) would call "forward", i.e. the direction the pilot's seat is facing.
There are a few aircraft, notably late Soviet designs like the MiG-29 and Su-27, that were engineered for desirable "post-stall" behavior. These aircraft are capable of remaining stable and controllable in extreme angles of attack (exceeding 90° off-chord) and are the best examples of an aircraft that can "fly backward", at least for a couple of seconds. The maneuvers involved include the tailslide (pull in to the vertical, stall nose-up, and fall back to earth tail-first, then pull back on the stick to kick your tail out behind you and drop the nose to recover) and the cobra (from full throttle, cut the engine and pitch up hard to intentionally stall the aircraft and rotate nose-up, then center the stick to allow the plane to nose-down). Most counterpart U.S. aircraft are incapable of these maneuvers as they're engineered to avoid stalling, following the "energy management" theory of Western combat maneuvering (where stalling, regardless of airspeed, means you're out of energy to maneuver, as you either have insufficient forward airspeed to maintain your turn, or you've just turned your plane's wings into air brakes).

The MiG-29 and the Su-27's post-stall behavior doesn't quite count as "flying backwards" so much as it "falling tail-first with some control effectiveness" (so much like being blown backward by a strong headwind I would say it probably doesn't count in the spirit of the question, since TBBT asked about using reverse thrust & presumably sustained flight). It is however impressive to watch!

In WW I, some German pilots perfected a technique to fly briefly backwards by stepping hard on one rudder pedal. The low directional stability and the impulse from the initial push would spin the aircraft through 360° around the vertical axis. But like the Su-27, this is less "flying" than a ballistic movement.

The first point of this answer is based on a naive (incorrect) assumptions about how wings work. Read What really allows airplanes to fly?. It is in fact very possible, for example to fly a plane with a symmetric aerofoil.

@NathanCooper: You both talk of different directions. While Keith means the direction in the plane of the wing, your direction is up or down.

In theory, yes, inefficient, very very unstable, with the control surfaces facing the airflow rather than behind it so a big risk of the airflow snatching the controls and forcing them over to full travel - with very bad results. The aeroplane would want to flick round and fly in the opposite direction because of the way its designed to fly forwards.

+1 for the theoretical 'yes'. The OP didn't specify theory vs practicality and you are the only answer that went there.

The more stable a design is in forward flight, the less stable it would be in reverse flight.  One could construct a plane with enough trimmable control surfaces to make it minimally stable in both directions, if one had some reason to want to do that, but it would be complicated and be unlikely to perform well in either direction.

When, as a youngster, I made model planes, I tried this. The result is very unstable and usually the tail lifts on launch causing the aircraft to flip over. I think that, with the use of computer control to counteract the inherent instability and a specially made propeller it might be possible but the development time and expense means that no-one would ever try to do it..
The problem is that the tail assembly of a standard configuration acts like a weather vane. It naturally wants to turn away from the direction of airflow.

There is a relation between the thrust provided by the engine and the lift created by the profile of the wings. Usually this relation is not the same backwards, so it will not fly backwards.
Propeller planes like the P-51 has an asymmetric aerodynamic profile that cannot provide the same lift moving backwards.
There is some aerodynamic profiles that are near to be symmetric, but requires a power plant much greater than a propeller. Usually this power plant cannot provide the same thrust backwards than forward.

It might be worth noting that since the propellor itself is an airfoil, it also won't produce nearly as much thrust when put in reverse.  So that would also impede the ability of the aircraft to fly backwards.

@JayCarr: It is the twist, not the airfoil, which makes the propeller so bad in reverse. The direction of airflow over the blades does not change, but the local incidence will be wrong over much of the blade span.

@JayCarr: Propellers are reversed by changing the blade pitch, not by turning them in the opposite direction.

@JanHudec Could the P-51 do that?  Eh, no matter, the P-51 was just an example and you're right of course, so...  There you go.  In my head I was thinking of planes with fixed props for some reason.

@PeterKämpf So...  Are you saying if the blades were reversed (as Jan Hudec says), they would still be less efficient because the twist is would be backwards at that point?

@JayCarr, no, I believe Peter was talking about twist because twist is why changing the pitch won't give you the same efficiency in reverse as you have forward. Because the twist is so that the pitch is higher in the middle where speed is lower, but when you go to negative pitch, the pitch will be lower (probably still positive) in the middle, so only the tips will produce thrust in the beta range.

@JanHudec Ah, I think I get it then.  Thanks!

If reverse thrust was generated (you couldn't do this simply by reversing the prop) then a plane could fly backwards.
While the wings are shaped to generate lift as they pass through the air in the forward direction, by using angle of attack and enough thrust you can generate lift in any direction. Angle of attack changes the apparent profile of the wing. The same principle allows planes to fly upside down or sideways in knife edge. The simplest example is how a paper plane can still glide with completely flat wings.

Please add for long you could fly backwards, given that all control surfaces will hard over into their stops and stability is negative around all axes.

Why would they be? Lift is still generated across the whole surface. Stability would be low, but the question was is it possible, not is it easy. :)

When the cg was ahead of the neutral point, it will be aft of it in reverse flight. The consequence is instability, proportional to the stability in normal flight. Remember that the neutral point is at the quarter chord, measured in flow direction.

@PeterKämpf I think the cg is close enough, it works on a model at least. But that is beside the point, my answer is mainly to highlight that the common misconception that wings only work because of their shape (and therefore only in one direction) is false.

You don't need reverse thrust to do this. Just pull the nose way up, and let the speed bleed off until your vertical speed is zero. Then you tailslide.
Most planes are designed to make this not very easy to do, but if you move the CG far enough back, by putting bricks in the tail, you can do it.
The trouble with that is, unless your plane is specially made, and you are specially trained, you will have a very difficult time not just sliding all the way to the ground (and voiding the warranty).

It's actually called a tailside and is a standard aerobatic maneuver

@rbp: corrected.

No.
Try riding your bicycle backwards down a steep hill if you are not sure what other writers here mean by passive pitch stability and yaw stability.
The reason why the big tail and elevators are well behind the middle of the wings is to make sure that when flying forward, they will tend to straighten any wobble.
Go to the pub and have a look at how darts fly if you want.  You can try throwing one of those backwards too.

This assumes that the bicycle and dart analogy extend to airplanes, so it is begging the question.

all_licenses: Creative Commons - Attribution Share-Alike - https://creativecommons.org/licenses/by-sa/4.0/


text:
Can I assume that AVGAS can be used without any problem when the engine manual suggests RON 95 or higher?
Can AVGAS 100 LL be used without any problem in Rotax 912i engine which suggests a fuel with RON 95 or higher? What would be the advantages of using AVGAS over unleaded RON 95 gasoline?

Why don’t you follow the Rotax recommendations: https://www.rotaxservice.com/rotax_tips/rotax_feed4.htm.  “ It is possible but not recommended to use 100LL AVGAS, since the the lead content is like cholesterol to your engine: it will accelerate wear on the valve seats, create deposits in the combustion chamber and sediments in the lubrication system and gearbox. Increased maintenance is necessary to compensate. Unlike “conventional” aircraft engines, lead is absolutely not essential to the proper lubrication and operation of a Rotax 4-stroke aircraft engine.
”

A small tidbit: the LL does stand for Low Lead, but the actual lead content is quite high, only in comparison with 100/130 was it low (half as much lead: 0.56 compared to 1.12). I have no source, but believe that 100LL is still around because the larger turbocharged engines in commercial usage cannot run on unleaded. Most smaller engines can, but it takes to much infrastructure to have to types of Avgas at most airports. The PA28-s I used to fly all used 91/96UL as we had it at the airport (Bromma, Stockholm).

Funny (or perhaps not so funny?) thing: "AVGAS" means "exhaust gas" in Swedish.

This question comes up regularly in automotive circles.
There is no advantage to using fuel with higher octane number than your engine requires, though in automobile engines there may be a minimum and an optimum (the car computer can adjust spark and, in recent years, valve timing to optimize efficiency, and will use higher compression and more advanced spark, both advantageous for power production and economy, on higher octane fuel).  This is not the case with any aircraft engine I'm aware of.
So, your Rotax 912i will gain nothing by using 100 octane avgas compared to 95 octane auto gas.  What you may find (assuming LL stands for Low Lead) is that the 100 LL will result in somewhat shorter spark plug life due to something automotive workers haven't had to think about in forty years: lead fouling.  Whether this is a problem or not depends on several factors, chief among them the type of plugs used in the Rotax 912i (polar gap or "conventional") and how long they're left in the engine before changing them.
Beyond the possibility of lead fouling, however, 100 LL avgas will not harm your engine (running 80 octane avgas might, on the other hand).  I'd suggest you run whichever is less expensive, keeps your engine cooler, or gives best power and/or fuel economy, as suits your needs.

"So, your Rotax 912i will gain nothing by using 100 octane avgas compared to 95 octane auto gas." Doesn't avgas have other properties with regards to temperature and pressure variations that makes it more suitable for use in aviation contexts, when compared to automotive gasoline? Even if it doesn't give your engine more power, it might help in other ways.

While it's true that avgas is always the same stuff while auto gas is reformulated regionally and seasonally, if the engine manufacturer has okayed auto gas, its variations won't cause trouble as long as the octane is at or above the requirement (though I'd certainly avoid using E85 to make the octane -- that's not even technically gasoline).  In practice, anything with a Rotax (i.e. experimental cert) isn't all that likely to get far enough from the pump before refueling for auto gas formula variations to cause trouble.

Yes it will run fine, but...
Lots of drag racers use Avgas in their cars to get the octane rating to run 12 - 14:1 compression ratios in high performance engines (At the airport I used to hang out at in the 70s, a Corvette owner that dragged his car would stop by every weekend to fill his car with the old green 100-130 octane fuel, because it was the only fuel he could use without blowing his engine up, his compression ratio was so high, and the car having old fashioned points ignition - no knock sensors or any of that fancy stuff).
But you can expect more frequent plug cleaning due to lead fouling (although this might be not too much of a problem with the 912's compression ratio).
The biggest thing to beware if is the oil. If you are a using full synthetic motor oil, this can be a problem because the polyalfaolefin base oils of synthetics are unable to hold lead combustion byproducts in suspension in the oil, and they will settle out in the engine instead in a sludge that coats the inside of the engine called "lead paint" (one tank full would be no big deal, but long term use could ruin the engine).
There was a big class action against Exxon Mobil years back by engine owners suffering from lead paint problems inside their engines (including a few failures from plugged oil galleries IIRC) after running them on Mobil AV1 full synthetic oil, which had to be withdrawn from the market (I used it briefly in my Cardinal).
The Aeroshell Multigrade oil line is only 50% synthetic (needs to have mineral oil in it because of the lead issues) and works well with avgas, and the other aviation oils are generally mineral based or no more than half synthetic.
So, bottom line is, if the engine has full synthetic oil (probably an automotive oil), it's ok in a pinch, but avoid running too much Avgas through it, and if it's mineral or semi-synthetic, should be no problems other than the potential spark plug issues.
Beyond that's there aren't really any advantages in the short term, unless you need the lower vapor pressure characteristics (higher boiling point) of Avgas (more resistant to vapor lock when it's really hot under the cowl) for very hot weather operation or operation at high altitudes and high temperatures, where mogas boils more readily.  The other one is long term storage.  With mogas it's a good idea to use fuel stabilizer if the plane will be parked for more than 6 months with mogas. Avgas being paraffin based, is very stable and can be stored for long periods without breaking down.
I use mogas in my Lycoming O-290 engine and it is much happier on that than on Avgas, which like to foul the lower plugs after only about 25 hours.

Any thoughts on running E85?  Ethyl alcohol is said to do better with higher compression but is bad for seals and tubing.  There may be ways around that.

You can use it safely if the fuel system is configured as you said and you will lose a bit of power and range.  Another minor problem is it's hydroscopic so you get more water absorption.  There was a guy promoting straight ethanol and used to fly a 150 around configured to run it in Canada about 20 yrs ago

@JohnK Isn’t hydroscopic safer in theory since the water won’t settle at the bottom? It’ll still hurt performance, but it shouldn’t cause total engine failure like it does with avgas, right?

I seem to remember that the problem is when the water content gets to some percentage of the alcohol, half a percent or one percent or something, the water/alcohol separates out from the gasoline.  And E-85 being 15% alcohol, it can absorb quite a lot of water and that's a lot of unburnable liquid to separate out.

I'd say the fuel feature ON indicates is its resistance to detonation, self-ignition, but energy content of AvGas being same as in any vulgar low ON gasoline, as the 85, or even 76 RON, the only available in some places. Detonation can destroy an engine very fast, but if the producer indicates your engine can work on ordinary fuel, using AvGas would add nothing but expenses to your flight.
The issue is very important, and in doubt about ON of the fuel they offer you, AvGas could be sometimes a good choice. Blessings +


text:
Why do my flights always use runway 24L at LAX airport?
I have taken several flights (in and out) from LAX (Los Angeles International Airport), both domestic and international and have flown in variety of commercial planes (727, 737, 747, 757, 777, 787, A319, A320, A330, A380, turboprops, etc). at various times of day but have always landed/taken off from runway 24L. According to Wikipedia, LAX airport has the following runways.

Runway
Length (ft)
Length (m)
Surface

6L/24R
8,926
2,721
Concrete

6R/24L
10,285
3,135
Concrete

7L/25R
12,091
3,685
Concrete

7R/25L
11,095
3,382
Concrete

I'm sure other runways are also used but why does 24L seem most preferred?

Two words: sample size. Eventually, you will use another one :)
There are only 4 runways, and they are all used heavily.
LAX normally has a westerly traffic flow, with aircraft landing/taking off toward the ocean.
How the airport operates:

At all times, the inboard runways shall be preferred to the outboard
  runways for departures

and

well over 90% of all operations use the preferred runways

Quotes from this document. Nice graphics can be found in there, too.

mmm.. That explains.. but don't you think its a bad model. One runway is having more "wear and tear" than the other.

@Ank inboards for departure, outboards for landing is a good model (and a common one).  It is much easier to queue departure aircraft that do not have to cross a runway and the arrival airplanes can be queued at different intersections to the departure runway and cross between departures.

ATC has a very specific flight path that they keep traffic inbound to LAX on.  If you are arriving/departing from/to a northerly direction then you will typically use the north runways.  The opposite is true for the south runways.  They also typically use the inner runways for departures and the outer runways for arrivals.  During less busy times they will allow aircraft to use a runway that is closer to their gate.

I'm flown Trans Pacific flights from LAX (flying east / west) and arrived / departed on 24L..

And last time I was flying to Chicago, departing from 24L and there was a Airbus A380 (Korean Air) departing from the same runway in front of me..

@Ank, from LAX, both Chicago and Korea are to the north, so 24L is preferred departure runway for both.

@Ank While you wouldn't normally think about it from looking at a map, the shortest path to Southeast Asia from almost anywhere in the mainland U.S. is North, not West. When I flew from LAX to HKG, we actually flew North of Alaska over the Arctic Ocean. We were so far North that we experienced midnight sun (it was near the beginning of summer.)

FWIW HKG is East Asia, not Southeast Asia.... Unless Mrs. Wright taught me wrong :)

Runway 24L appears to be closest to the terminals.
I was heard, don't know if it's true), that LAX uses the inner runways (24L / 25R, 06R / 07L) to land and the outer runways to takeoff from (24R / 25L, 06L / 07R)

There are 8 terminals in LAX. I can't believe 24L is closest to all. Its a long taxiway for United Airlines to 24L but it still takes off / lands on 24L.

You sure LAX uses 06L, 06R, 07L, 07R). For a large airport like LAX, I'm not sure if it'd take off / land on both sides of runway.

Depending on the wind direction, the aircraft will use either the runways to the west or the runways to the east.  They never takeoff and land in opposite directions.

KLAX under normal operations will depart 25R and 24L (The "inboards") and land 25L and 24R (outboards). The same applies true for the rare days KLAX is in east flow. This is for several reasons, but the primary one is so that there is only ONE runway crossing and that occurring as far downfield for safety.  Typically if you are arriving/departing from/to the NW, you will be on the north complex, SW CCW SE the south complex and it's a mix if you are going E/NE.  In some cases, heavy freighters or LONG haul pax flights NEED 25L as it is the longest runway for performance reasons.  24R is currently only 9630' due construction.


text:
What is missing from a non-afterburning engine to prohibit the use of afterburning?
What components are missing in a non-afterburning engine that an afterburning engine does, so that it can't use afterburning?

good one, I mean what components.

You might get a better response by asking the opposite. i.e. What components are required.

@anonymous What components? The afterburner. Seriously, you're asking a tautology.

@Notts90 The required component would be an afterburner. A better question would be "how do afterburners work?" but that's already answered on Wikipedia.

@DavidRicherby the afterburner is more than one component. Not much more but still more.

What is missing from a non-turbocharged engine to prohibit the use of turbo boost?

The afterburner, of course.
In simplest sense, the afterburner is just an extension attached to the engine where the fuel is dumped into the exhaust, resulting in an inefficient but huge increase in thrust.

Turbojet with and without afterburner; image from aerospaceweb.org
In the above image, you can see the basic schematic of the afterburner- it basically consists of a long tube placed in between the turbine and the nozzle in which additional fuel is added and burned. The (afterburner) tube is quite simple, consisting of mechanisms to spray fuel into the exhaust and ignite it.
This image shows an actual afterburner, from the F/A -18 (F404 engine). As you can see, its quite simple.

... sailor Ryan Draper ... inspects an F/A-18 afterburner in the jet shop aboard the Nimitz-class aircraft carrier USS George Washington (CVN 73). Image from gizmodo.com

About your point on efficiency: as I learned doing the equations in college, the thermal efficiency (a ratio) increases when in afterburner, but so does the fuel consumption (significantly) which reduces the "MPG" for the aircraft.

In simplest terms, an afterburner is just an inefficient bolt-on rocket engine.

How is the afterburner duct designed and why is the tube so long?  Is its role and design trivial or is it very different from a non-afterburner nozzle?

@CodyP The duct essentially acts as a rocket engine combustion chamber.  A jet can't burn all the oxygen it ingests without overheating so the leftovers get burned downstream to "reheat" the exhaust gas and increase its exit velocity.  The length is required to allow sufficient combustion of the injected fuel and the design, as with most things in aerospace, is really not trivial (at least in real implementations).  The nozzle has to be sized (and able to expand in afterburning mode) to prevent backpressure that can cause a compressor stall in the turbine.

@CodyP: The length of the afterburner is basically an open ended oven. If the tube is short all you'll be doing is dumping unburnt kerosene out the tail end of the engine.

Also additional control gear to decide to dump fuel in, and control the variable area nozzle (which can be fixed area in a normal engine)


text:
Travelling at faster than mach 1, how sharp could Concorde turn to avoid injury to passengers?
To avoid injury to passengers (too many G's) was there a max 'sharpness' of the turns it made when travelling at certain speeds?

It didn't make turns of any significance when flying supersonic (no commercial aircraft makes significant turns in cruise). When it was making significant turns when departing and arriving, it was flying at the same kind of speeds as any other aircraft.   In any case, when turning at a given bank angle, the speed has no impact on the G force felt. Rather, the turn radius increases.

Crew flying passenger transport aircraft—whether super or sub-sonic— generally limit the aircraft bank angle to 30° or less. A level turn at a given bank angle will result in a specific corresponding load factor—or G-loading—regardless of speed. A level turn at 30° of bank at any speed will yield a load factor of only about 1.2 (1.2 Gs, as opposed to the normal 1.0 Gs). This is fairly imperceptible.

@ymb1 SR-71 was not a passenger aircraft ;-)

Most airliners will disintegrate before an injury caused by a sustained G can be inflicted. (Most people will easily bear 3G, while most airliners won't (though won't necessarily disintegrate yet)). Injuries may happen because of a sudden force, but this doesn't normally happen when entering a turn.

I once read that the sr71 took most of North Dakota to turn around at cruise. Mach 3, military pilots. Bank angle?

All aircraft experience the same G force per degree of bank angle, so a 60 degree turn in a Cessna produces 2G just like a 60 degree turn in Concorde would produce 2G.
The difference is that a Cessna doing 100 knots could circle in 0.2 miles by using a 60 degree bank angle.
Concorde doing 1000 knots and 60 degrees would take up 19.5 miles to do the same thing.
In both cases the passengers would experience 2G which even so is pretty severe if you are a passenger and aren't used to it. It would get your attention let me put it that way.
I'm not an airline pilot. However I would think that the risk with higher speeds is in angle of attack or angle of attack combined with bank angles. At higher speeds its much easier to produce a whole load of G by pulling or pushing the controls than it is in your Cessna, and even that can be pretty severe.
So while you might not worry as much about bank angles you would be very careful not to pitch up or down too far especially at higher speeds because you could overstress the aircraft real easy.
Hopefully a pilot who knows Concorde and / or airliner systems can improve on this answer.

The math to verify Mr. Philip Johnson is given below. The maximum bank angle for a normal category aircraft is 60deg at 2G's. The formula for turn radius is
$R  = \frac{V^2}{G\cdot tan(bank)}$
given
$V = 168900(ft/sec) = 1000kt \cdot 1.68$
$G = 32.2(ft/sec)$
$tan(bank) = 1.7(60deg) $
$R = (1690^2) / (32.2 * 1.7) = 52175(ft) = 9.8mi$
$19.76.4mi$ diameter = $9.8(radius) \cdot 2$

Well, the maximum operational bank angle of airliners is nearer 30°. Pulling more than 1.15gs is frowned upon among airline pilots.

I couldn't agree more. I used the 60 degrees of bank in my example because I wanted to show that large angles of bank on its own shouldn't cause too many problems even at high speed, but pitching most definitely will. Also everything gets so sensitive at higher altitudes and speeds and the aircraft needs finer control. Is that because you are deeper into coffin corner where Vne meets stall speeds? Sorry maybe I should ask a question..

I am a pilot and A&P. 30 degrees is not a regulation, it is a recommendation by the FAA for passenger comfort on commercial operations and a safety consideration for IFR flights (the higher the bank angle, the higher stall speed and harder controlability). 60deg is the legal maximum an aircraft is allowed to be banked unless certified for aerobatic maneuvers. 60deg of bank is the required for certification under the "normal" category of all aircraft - they must have a structural load limit of 4.7g which gives a safety factor of 2x or about ~2g more than would be encountered in legal maneuvers.


text:
Can anyone explain why and how flames shot out of an F/A-18 as it crashed?
Can anyone explain why and how flames have shot out of the left engine of this F/A-18, whose left engine was apparently not generating power, the picture is here. And the source website where I got the infomation from is here.
The accident happened in Lethbridge, Canada in the July of 2010. Below is a comment posted on the forum in response to the post of the crash on ED forums:

It was a fuel control problem (sticky piston) on the right engine, isn't #1 the left? The open nozzle of the left engine indicates that it's either a) at idle or b) at full power/burner which it was in this case as the pilot was executing a high alpha pass at the time.

The comment about the left engine not hasving power is here:

The left engine has the nozzle fully open, showing that #1 engine was developing no power.

Looks like the right engine to me.

@GregTaylor it is the left, it crashed with its canopy/cockpit facing the camera

It looks like this incident involving a Canadian CF-18, considering the angle of the picture and the runway signs. There is also this video of the crash. Apparently the right engine was out of fuel and the Pilot was applying afterburner. Could be a leak of fuel that was ignited upon impact. Other users might know more about it.

Fuel has to reach the engine to make it work, so there is a path (pipes) available for the fuel to get from the tanks into the engines.
Looking (*) at the video linked by Pierre Chevallier it looks like some fuel got pressed out of the tanks, into the engine(s) and out the engine nozzle, and in the process it got ignited.
I cannot say why the fuel got only in one engine, I can guess that the valves on the fuel lines were in different positions.
(*) I suggest using the option to visualize at x0.25 speed, starting at the 0:30 mark

From the report: The engine malfunction was likely the result of a stuck ratio boost piston in the right engine main fuel control (MFC) . It seems your guess is right.